Wide band antenna



Oct. 7, 1941. p. s. CARTER 2,258,406

WIDE BAND ANTENNA Filed Apiil 16, 1938 2 Sheets-Sheet 1 INVENTORQ P/-/IP 5. CARTER 06f. 7 1941. I s CARTER 2,258,406

WIDE BAND ANTENNA Filed April 16, 1938 2 Sheets-Sheet 2 I NV EN TOR.

v 5%IP 6. CARtER BY may TORNEY Patented Oct. 7, 1941 Philip s. Carter;Port Jefferson, N. Y., assignor t 7 Radio Corporation of America; acorporation of V Delaware A plication Aprilll G, 1938, Serial No.202,460

Claims. (01; 2511- -33) t The present inventionrelates to antennas and,more particularly, to, antennas for: use with Wide band televisionreception and transmission.

The primary object of the present invention is to provideI an efiicienttelevision antenna for transmission or reception of horizontallypolarized waves which may be easily and simply erected. t t Anotherobject is to provide a television antenna for transmission or receptionof horizontally polarized waves which is substantially nondirectional. Vt

s till another object of the present invention is to provide a simplebroad band antenna which may be directly connected to a transmissionline. The most commontype of antenna used for transmission and receptionof horizontally polarized waves is a horizontal half wave dipole. Theradiation pattern for this typ of antenna is a figure of 8 in thehorizontal plane, the radia-' tion being zero in directionscorresponding to the axis of theantenna, This type oiantenna requiresthe use of an auxiliary circuit when its impedance is matched to atransmission line.

The present invention overcomes the above mentioned objectionableradiation and frequency band characteristics while still maintaining thesimplicity of the commonly used half wave dipole.

Brieflyymy invention consists of an antenna comprising two conductorarmsforming an angle oi SQdegrees with each other, having a transmissionline connected to theirapex, and supported at their non-adjacent ends bymeans of insulators connected :to any suitable supports. The conductorsmay be either a quarter or a half wave in length and they may each be asingle wire or each comprise. a plurality of parallel wires connected inseries. If a plurality of wires are used the wires are very closelyspaced. perhaps a one-hundredth of a wavelength apart. The radiationpattern of such an antenna in the plane, of the conductors does notappreciably depart from a circle, in the case, of an antenna havingquarter wave length arms the minimum field strength being about 71percent of that of themaximum so thati for practical purposes it shouldbe useful for reception in any direction, In the case of an antennahaving half. wave length arms the minimum is somewhat smaller. On thother hand, the impedance of such an antenna is somewhat higher reducingdifficulties in matching the antenna to a transmission line.

A better understanding of the invention is to; be had by referring tothe following detailed deprises, as shown in this figure, two conductorsA andB, lying in a substantially horizontal plane, each a quarter of aWave in length and forming an angle of 90 degrees with each other. Attheir apex a transmission line TL is connected. The non-adjacent ends ofconductors A and B are supported by means of insulators I which areconnected to any convenient supporting struc-' ture (not shown). If itis desired to connect the antenna to a two wire transmission line havinga somewhat higher impedance than that usable with the embodiment shownin Figurel, the modification shown in Figure 2 may be used. By thescheme shown in this figure the impedance of the antenna may betransformed to a valuefour times that of a simple two-Wired V. In thismodificationconductors A, A and B, B are very closely spaced from oneanother, perhaps a distance of one one-hundredth of a'wave length andare electrically connected at. their ends. The currentsfiowing in thetwo 6011-. ductorsfwill be in the same direction in space, although inopposite directions withinthe antenna circuit due tophase reversal atthe ends. Consequently, the arrangement will be almost identical in itsradiation characteristic with that of the single wire antenna shown inFigure 1. However, as previously pointed out, the re sistance will befour times that of the simple two wire v.

,In the. modification shown in Figure 2 it has been assumed that theconductors are of the same diameter. This does not have to be the case,however, andif desired the conductors may have different diameters,particularly in cases where it is desired to depart from an eventransformation ratio. By making the. diameters of the 'two. wires A, A,B, B unequal, as shown in Figure. 3, almost any desired. transformationratio may be obtained.

. When conductors of different diameters are employed in the antennasystem it will be found that. the. conductor of larger diameter willcarry the larger current. i The difference in the amount of currentcarried by the conductors of difierent diameters results in a differenttransformation ratio from the case where theconductors are of the samediameter. The reason the larger diameter conductor carries a greatercurrent than the smaller diameter conductor in the antenna system is dueto the fact that the larger diameter conductor has less series reactancefor unit of length than the smaller diameter conductor. Obviously, ifdesired, conductors A and Blmay be made larger in diameter thanconductors A, B. The eifect of this change is to make the transformationratio less than that of a similar antenna system where the conductorsare of the same diameter.

Figure 4 illustrate approximately the radiation pattern obtained withthe embodiments of my invention shown in Figures 1, 2 and 3 wherein thearms are each a quarter wave in length.

Figure 5 illustrates a further modification of my invention wherein theconductors A and B are each a half wave in length. Otherwise, thisfigure is exactly the same as in Figure 1.

With the antenna constructed in this manner there is more variation infield strength with direction than with the first type but thismodification has a higher radiation resistance which is an advantage inmatching the antenna to the usual type of transmission line.

As shown in Figure 6, it is also possible to obtain different inputimpedances with the antenna having half wave length arms by adding asecond pairof conductors ,A, B to the system. These conductors arearranged inthe same way as de-' scribed for Figure 2. However, in thisembodimerit the conductors A, B' must not be connected inthe center, forif this'were done the currents in the two conductors-would be equal andopp site and the radiation resistance of the system would be negligiblysmall. p

Figure '7 shows the approximate radiation patinto effect, myinvention'is by no means limited 3. In an antenna system comprising apair of separated conductors having a length equal to a quarter of thelength of the operating wave and forming an angle of 90 degrees witheach other and a, transmission line directly connected to the adjacentends of said pair of conductors for energizing said conductors in phaseopposition, means for multiplying the impedance of said antenna to avalu equal to that of said transmislength as said first pair arrangedparallel to said first pair of conductors and closely spaced therefrom,the adjacent ends of said second pair of tern obtained using theantennas shown in Figto'the particular arrangements shown and describedand modificationsmay bemade' without departing from the scope and spiritof the invention. v 1 I claim:

' 1;In an antenna system comprising a pairof separated onductors formingan angle of 90 degrees with each other and means for energizing saidconductors in an opposing phase relationship comprising atransmission'line' directly connected to the adjacent ends of said pairof conductors, means for matching the impedance-0f said an-" tenna tosaid transmission line over a wide band of frequencies comprising asecond pairofcone ductors of the sam length as said first pair arrangedparallel to said first pair of conductors and closely spaced therefrom;said second pair of conductors being connected to said first pairatpoints removed from said adjacent ends, whereby there is minimized theexistence of refiected waves on said transmission line which mightdisturb the radiation antenna conductors. Y 7

I 2. In an antenna system comprising a pair of separated conductorshaving a length equal to characteristics of said a multiple, includingunity, of a quarter of *the length'of the operating wave'and forming'a-horizontal angle of 90 degrees with each other, and atransmission linedirectly connected to the adjacent ends of said pair of conductors forenergiz ing lsaid conductors in phase opposition, means for matching theimpedance of said antenna to said'transmissionlline over 'a wide band ofire-'- quencies comprising a second pair of conductors arranged parallelto said first pair of conductors and closely spaced therefrom, saidsecond pair of conductors being connected tosaid first, pair at, pointsremoved from said adjacent ends, whereby there is minimized theexistence of refiected waves on said transmission line which mightdisturb the radiation characteristicsof said antenna conductors. v

conductors being connected together, said second pair of conductorsbeing connected to said first pair at points removed from said adjacentends and said second pair of conductors havinga different diameter thansaid first pair whereby said impedance multiplication is an odd value,whereby there is minimized the existence of -re'- fiected waves on saidtransmission line which might disturb the radiation characteristics ofsaid antenna conductors. J

4-. ;In an antenna system comprising a pair of separated;conductorshaving a length equal to a quarter of the length of the operating waveand forming a horizontal angle of 90 degrees with each otheran'd atransmission line directly conn'ectedto the'adjacent'ends of said pairof conductdrs for energizing said conductors in phase opposition; meansfor multiplying theim-pedance of said antenna to a valueequal to that ofsaid transmission-line whereby reflection of energy into saidtransmission line is prevented compris inga second pair ofconductors ofthe same length as said first pair arranged parallel to-said firstpairof conductors and-spaced therefrom adis= tance of the order of 1/100of the operating wave length,"the adjacent ends of said second pair ofconductors being-connected together, said second pa'ino-fconductorsbeing connected to said first pairat points removed from said adjacentends and said second pairof conductors being ofthe same diameter as saidfirst pair of conductors;

i1 "5;"In an antenna system comprising-a pair of separated conductorshaving alength equal to half the'length of the operatingwave and forming'a horizontal angle of 90"degrees with each other; and atransmissionline directly connected to the adjacent ends of saidpair of conductorsfor energizing said conductors in phase opposition, means for matchingthe impedance of said antenna to the-impedance of said transmissionline. over a wide band-of frequencies whereby reflection is preverte'dcomprising a second pair of conductors of the same length as said firstpair arranged parallel to said first pair of conductors andcloselyspaced therefrom, said second pairof conductors being connected'to saidfirst pairflat points removed from said adjacent ends, said second pairof conductors having a different diameter than said first pairlwherebythe impedance change due to saidsecond pair is an odd multiple, wherebythere is minimized the a existence of reflected waves onsaidtransmission line which might disturbthe radiation charac-.

PHILIP s. CARTER.

